gdb/

	* target.c (update_current_target): Change the default action
	of 'to_traceframe_info' from tcomplain to return_zero.
	* target.h (struct target_ops) <to_traceframe_info>: Add more
	comments.
	* valops.c (read_value_memory): Call
	traceframe_available_memory unconditionally.

gdb/testsuite/

	* gdb.trace/read-memory.exp (test_from_remote): Update test.
	(teset_from_exec): Likewise.

1 files changed, 12 insertions, 3 deletions

diff --git a/gdb/target.h b/gdb/target.h
index 2ba85d9..21e5792 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -854,9 +854,18 @@ struct target_ops
       (const char *id);
 
     /* Return a traceframe info object describing the current
-       traceframe's contents.  This method should not cache data;
-       higher layers take care of caching, invalidating, and
-       re-fetching when necessary.  */
+       traceframe's contents.  If the target doesn't support
+       traceframe info, return NULL.  If the current traceframe is not
+       selected (the current traceframe number is -1), the target can
+       choose to return either NULL or an empty traceframe info.  If
+       NULL is returned, for example in remote target, GDB will read
+       from the live inferior.  If an empty traceframe info is
+       returned, for example in tfile target, which means the
+       traceframe info is available, but the requested memory is not
+       available in it.  GDB will try to see if the requested memory
+       is available in the read-only sections.  This method should not
+       cache data; higher layers take care of caching, invalidating,
+       and re-fetching when necessary.  */
     struct traceframe_info *(*to_traceframe_info) (void);
 
     /* Ask the target to use or not to use agent according to USE.  Return 1